Structures And Properties Of Metal-Organic Frameworks Based On The Rigid Ligand(1,1'-Biphenyl)-2,4,6-Tricarboxylic Acid

Metal-Organic Frameworks(MOFs)generally are compounded by metal ions and ligands as nodes,and they are combined through coordination bonds or other forces to form networks of potential porous structures.MOFs are usually designed into structures with high porosity and specific surface area due to their flexible pre-design and post-modification properties,which lead to their wide applications in gas adsorption and separation,fluorescence doping detection,magnetism and other aspects.In recent years,MOFs have attracted extensive interest in architecture,crystallography and performance development.However,how to build MOFs with multiple functions at the same time remains a challenge.In this paper,the rigid ligand 1,1'-biphenyl-2,4,6-tricarboxylic acid(H₃bptc)was selected as an organic linker to construct the target complex with metal ions.Its advantage lies in that H₃bptc is a derivative of trimesic acid(H₃btc),and its flexible carboxylic acid group can support the coordination environment around-O-groups and the variable coordination mode with various metals.Particularly,the introduction of benzene will lead to the change of coordination mode and channel size.Seven complexes were successfully synthesized by solvothermal method using H₃bptc and different metal ions:{[Cd(Hbptc)]·H₂O}_n(Cdbptc),{[Ln(bptc)(H₂O)₃]·3H₂O}_n(Ln=Eu,Tb,Gd)(Lnbptc),{[Cu(Hbptc)]·2H₂O}_n(Cubptc1),{[Cu(Hbptc)(H₂O)₂]·2H₂O}_n(Cubptc2)and[Mn(Hbptc)(H₂O)₃(DMF)]_n(Mnbptc),the seven cases of MOFs were characterized by chemical and physical methods.Following studies have been conducted:1.The development process,synthetic types and methods,specific applications,the purpose of topic selection and the main achievements of MOFs are briefly introduced.2.The coordination polymer Cdbptc was prepared by the ligand H₃bptc and the transition metal ion Cd²⁺through solvothermal reaction,and the ability to catalyze the cycloaddition reaction of CO₂ was studied.At the same time,Cdbptc showed the ability to selectively detect five ions:Cu²⁺/Fe³⁺/Cr³⁺/[Fe(CN)₆]^3-/Cr₂O₇^2-,especially the detection limit of Cr₂O₇^2-reached 10^-6.In addition,due to the porosity of Cdbptc(pore size 14.945?×17.760?×14.080?),it has the selective adsorption and separation ability for the organic dye methyl green,and the corresponding mechanism was explored.3.Three isomorphic lanthanide MOFs were synthesized by the ligand H₃bptc and lanthanide metal ions Eu³⁺,Tb³⁺and Gd³⁺.Then,MOFs with 13 colors and tunable emission patterns were obtained by adjusting the proportion of two different metal ions in the synthesis reaction process,and the above tuned MOFs were used to make the security code of quick response code.At the same time,H₃bptc is doped with a certain proportion of Eu³⁺,Tb³⁺and Gd³⁺ions to self-assemble into a white emitting trimetallic MOF.It was found that nitrobenzene and acetone showed quenching effect on Tbbptc by fluorescence test,and the mechanism of quenching was discussed.4.Two metal-organic frameworks Cubptc1 and Cubptc2,containing binuclear metal clusters,were constructed by H3bptc and transition metal ion Cu²⁺.In addition,Mnbptc with3D structure frame was also self-assembled by H3bptc and Mn²⁺.The basic physical and chemical characterization of three MOFs were determined,and the magnetic properties of the three MOFs were systematically tested.The MOFs all showed anti-ferromagnetic exchange effect.